Magnetic properties of Co[sup II] mesoclusters

Sato, Michi; Takada, Syozo; Kohiki, Shigemi; Kohiki, Shigeni; Babasaki, Tomohiro; Deguchi, Hiroyuki; Oku, Masaoki; Mitome, Masanori
August 2000
Applied Physics Letters;8/21/2000, Vol. 77 Issue 8
Academic Journal
Clusters of cobalt (II) ions dispersed in a mesoporous silicate, prepared by calcination of the MCM-41 molecular sieve soaked in CoCl[sub 2] 0.01 mol/l aqueous solution, showed no x-ray diffraction peaks except one from the molecular sieve. X-ray photoelectron spectroscopy and ultraviolet-visible diffuse reflectance spectroscopy revealed that the mesoclusters consisted of Co[sup II] ions in tetrahedral coordination. We have observed temperature and frequency dependences of the alternating current susceptibility, and no divergent peaks of the nonlinear susceptibility due to superparamagnetism. Spins derived from the field dependent magnetization above the blocking temperature with the Langevin equation fairly agree with those at the cluster surface estimated from the ionic radii of Co[sup 2+] and O[sup 2-]. © 2000 American Institute of Physics.


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